Kissing your best friend’s boyfriend was not your smartest move. Your best friend is justifiably hurt and angry. You must make an effective apology if you want the relationship to survive this blunder. It might take her a few days to simmer down enough to talk to you, but when that occurs, ask for an opportunity to apologize and make amends.

When making an apology, take full responsibility for your actions. Casting blame on your best friend, her boyfriend or any other person diminishes the value of the apology, according to psychiatrist Aaron Lazare in “Making Peace Through Apology” on Greater Good. Admit what you did without an excuse. You could include an explanation, such as expressing appreciation for something he did for you, but that should in no way shift the blame for your actions.

Your heartfelt apology must let your best friend know that you understand what you did was wrong and that the offense won’t happen again. You might say, “I should never have kissed him for any reason and I promise I won’t kiss him again.” Acknowledge that the kiss violates the ethics you expect of yourself and that your friend expects of you, suggests psychologist Guy Winch in “The Five Ingredients of an Effective Apology” for “Psychology Today” online. Include the full extent of your offense, such as admitting that she was hurt, disappointed, angry and perhaps humiliated and shamed by your actions.

Making reparations when something tangible is lost is an easy call -- you replace or repair it. When the loss is dignity, honor or trust, it’s harder to know what will make things right. The purpose for this apology is easing your best friend's hurt and should focus on her needs and feelings, asserts Winch. If you aren’t sure how to make things right, ask her what you can do, suggests sociologist Martha Beck in “The Right Way to Apologize” on Oprah.com. Your best friend will know what she needs in addition to having her feelings acknowledged.

The last step in your apology is to ask for forgiveness. Forgiveness is never a given and you should let your best friend know that you don’t expect her to forgive you, advises Beck. You could say, “I have no right to expect that you will forgive me, but I hope that there is some way I can remain your friend.” Unlike dealing with your child on the playground, you can’t expect to kiss and make up. Accept that it might take time before your friend trusts you again.